1. Field of the Invention
This invention relates to a system for controlling multiple video cameras. This invention allows for an automated camera handoff for selecting and directing cameras within a multi-camera system, as might be used in a security system or a multi-camera broadcasting system. The automation is provided by tracking a figure within the image from an individual camera, coupled with an area representation of the fields of view of each of the other cameras.
2. Description of Related Art
Security systems for airports, casinos, and the like typically employ a multitude of cameras that provide images of selected areas to a control station. The images from each of these cameras, or a subset of these cameras, are displayed on one or more monitors at the control station. The operator of the control station is provided an ability to select any one of the cameras for a display of its image on a primary monitor, and, if the camera is adjustable, to control of the camera""s field of view. Such control systems are also utilized for selecting from among multiple cameras at an event being broadcast, for example, multiple cameras at a sports arena, or studio.
The selection and control of the cameras is typically accomplished by controlling a bank of switches, or by selecting from amongst a list of cameras on a computer terminal. To view a particular area, the operator selects the camera associated with that area. If the camera is adjustable, the operator subsequently adjusts the selected camera""s field of view by adjusting its rotation about a horizontal axis (pan) or vertical axis (tilt), or its magnification (zoom). The entire span of an adjustable camera""s span of view is termed herein as the camera""s potential field of view, whereas the view resulting from the particular pan, tilt, and zoom settings is termed the camera""s actual field of view.
Image processing algorithms are available which allow for the identification of a particular pattern, or figure, within an image, and the identification of any subsequent movement of that figure. Coupled with a security control system, such image processing algorithms allow for the automated adjustment of a camera so as to keep the figure in the center of the cameras actual field of view. When the figure travels beyond the potential field of view of the camera, the operator selects another camera whose potential field of view contains the figure at its new location, adjusts the camera, identifies the figure in the camera""s actual field of view, and thereafter continues the automated tracking until the figure exits that camera""s potential field of view.
In the conventional camera selection scenario, the operator must be familiar with the layout of the secured area, as well as the correspondence between the displayed image and this layout. That is, for example, if a figure is seen exiting through one of several doorways, the operator must be able to quickly determine to which other area that particular doorway leads, and must further determine which camera includes that other area.
It is an object of this invention to provide for the automation of a multiple camera system, so as to provide for a multi-camera figure tracking capability. The preferred system will allow for the near continuous display of a figure as the figure moves about throughout the multiple cameras"" potential fields of view.
The approximate physical location of a figure is determined from the displayed image, the identification of the figure within this image by the figure tracking system, and a knowledge of the camera""s location and actual field of view which is producing the displayed image. If the figure exits a selected camera""s field of view, another camera containing the figure within its field of view is selected. The bounds of each camera""s potential field of view are contained in the system. The system determines which cameras"" potential fields of view contain the figure by determining whether the figure""s determined physical location lies within the bounds of each camera""s field of view.
In a preferred embodiment, when the figure approaches the bounds of the selected camera""s potential field of view, the system determines which other camera""s potential field of view contains the figure, then adjusts that other camera""s actual field of view to contain the figure. When the figure is at the bounds of the selected camera""s field of view, the system automatically selects an other camera and communicates the appropriate information to the figure tracking process to continue the tracking of the figure using this other camera.
In a further embodiment of the invention, the system also contains predictive location determination algorithms. By assessing the movement of the figure, the selection and adjustment of the next camera can be effected based upon the predicted subsequent location of the figure. Such predictive techniques are effective for tracking a figure in a secured area in which the cameras"" fields of view are not necessarily overlapping, and also for selecting from among multiple cameras containing the figure in their potential field of view.
By associating the displayed image to the physical locale of the secured area, the operator need not determine the potential egress points from each camera""s field of view, nor need the operator know which camera or cameras cover a given area, nor which areas are adjacent each other.
In another embodiment, the selection of a target is also automated. Security systems often automatically select a camera associated with an alarm, for the presentation of a view of the alarmed area to the operator. By associating a target point with each alarm, for example the entry way of a door having an alarm, the system can automatically select and adjust the camera associated with the alarm to contain that target point, and identify the target as those portions of the image which exhibit movement. Thereafter, the system will track the target, as discussed above.